The {% page_attribute %}
tag is used by the cms to render the page's meta and other properties.
This tag will not work for newsblog articles as they are a different object.
I suggest to wrap the {% page_attribute "meta_description" %}
call in a block on your page base template:
{% block meta %}
<meta name="description" content="{% page_attribute 'meta_description' %}">
{% endblock meta%}
Then in your article base template you can do something like:
{% block meta %}
{% if article %}
{# rendering article detail page #}
<meta name="description" content="{{ article.meta_description }}">
{% else %}
{# rendering article landing page #}
{{ block.super }}
{% endif %}
{% endblock meta%}